Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
Click on an image to view a larger image, and
click the
browser's BACK button to return back to the
page.

Day 71 - FTC flights

Photon ready for its maiden flight.

We set the deploy delay to around 4 seconds.

High speed take off at 100psi.

The deploy delay was a little too long.

"C'mon dad can I launch it yet?"

Higher speed take off at 160psi.

Getting closer to the correct time setting.

The small parachute prevents drift.

Setting up for third flight.

At 180 psi the deploy timing was fairly
close to ideal.

Rocket all pressurised and ready to go on
the fourth flight.

Although you could not see it at the time,
and the rocket went fairly vertically, this
photo shows the forces involved on take off.
Inspecting the rocket post flight showed no
damage.

Parachute tangled soon after deploy but
opened in time to save the rocket.

A great action shot.

Without guide rails the Tachyon rocket took
off at a bit of an angle. Launched at 140 psi.

FTC Flights

Since we could not make it to the last NSWRA
launch day, and then the cancelling of the
NSWRA picnic due to bad weather we haven't
been able to test fly our first FTC rocket.
This Sunday, however, the weather was
perfect with no wind, mild temperatures and
dry ground, and so we went to our old launch
area at Denzil Joyce oval. We wanted to see
how well all the systems on the rocket were
going to perform since we hadn't built a
rocket like this before. The aim was to
reduce the launch pressure to keep the
rocket within the park.

We also brought along some of our other
rockets as backups in case the FTC rocket
lasted only one launch. All in all it was a
great day for flying rockets, and all
rockets performed well and landed without
damage.

We also tested for the first time the
Assemtech G-switches as well as our
RCA plug
G-switches. The Assemtech G-switch will
be an optional component for V1.6 of the FC.

Launch Day Events

We arrived at the oval just before
7am, and the set up time was quick since we
didn't need to bring any cover, chairs
or tables. The launcher was also easier
to set up since the guide rails weren't
needed for the FTC rocket (and Axion II) as
the launch tube acts as the guide rail.

For the first FTC flight we set the
deploy time delay to around 4 seconds
and only pressurised the rocket to
100psi since we had no idea what the
rocket would do or if the parachute
deploy mechanism would fail under the G
forces. The rocket went up very well and
straight and the parachute opened well
past apogee. It only reached 198' (60m).

We were happy that the split nosecone
deployment mechanism worked well, and
dad even managed to catch the rocket on the way
down. No breeze meant it landed close to
the launch pad.

Encouraged by good flight and
proximity of the landing to the launch
pad, we left the time setting as it was
and pressurised the rocket again but
this time to 160 psi. The rocket again
went up nice and straight and this time
reached 341' (104) m. The parachute
deployment happened closer to apogee
this time. Dad managed to catch the
rocket again before it landed.

On the third flight we increased the
pressure to 180 psi and also added more water as that was what the
simulator was predicting as the optimum.
The rocket took off nice and fast and
what appeared fairly straight. This time the
parachute opened right around apogee so
we had the timing set correctly. The
rocket reached 370' ( 113m ).

As we started pressurising the
rocket for the fourth flight it popped
up ever so slightly in the release head
- perhaps a couple of mm, but that was
enough to trigger the launch detect
G-switch and the parachute popped off.
It's nice having the safety abort
pressure relief valve for these
instances. We repacked the parachute and
pressurised it to about 20 psi before
arming again. The little bit of pressure
ensures that the rocket is full up
against its stops so there is no
vertical movement.

The fourth flight was almost
identical to the previous one reaching
an altitude of 373' ( 114m ). The
parachute deployed around apogee, but it
looked like it became tangled on the way
down. It finally fully opened at around
130 feet AGL. We will need to see if
there is a better way to pack the
parachutes and lines. We did learn that
the payload and parachute attachment
points as well as the thin Kevlar cord are strong enough to handle the
higher speed deploys.

All in all we were very happy with the
FTC flights.

We then decided to launch some of
the smaller rockets for the kids. We
used our original small launcher as that's
all that is needed for the small
rockets. We launched the
Neutrino rocket
as well as
Clifford. We hadn't launched
the Clifford rocket for almost 2 years
so it was fun to do a bit of retro
rocketing. The rockets survived well,
and kids got enjoyment out of seeing
them fly.

Tachyon IVb was launched with foam and
at 140 psi. The rocket used one of our
new G-switches so it was a good test for
it. The rocket flew well and went pretty
high but landed fairly close to the
road, so we set that one aside. Foam is
always unpredictable.

The Axion rocket uses a 15mm nozzle and
the launch tube. We removed one of the
spliced pair sections to reduce its
volume and only filled it to 100psi,
again to keep it in the park. The rocket
flew very straight and very high. It
would have been close to the 110-120m mark
but without an altimeter that's only a
guess. The rocket landed without
incident. It also used our new RCA G-switch
so we are confident that it is working
well.

We packed up and were off the oval
by 9am. It was nice to be able to get 9
launches in in a two hour window. We would
normally only achieve half of that in a
whole day at Doonside due to the
necessary launch windows when so many
people fly at the same location.

Observations

The Assemtech G-switch seems to be
working well for the FTC rocket. We
still need to test it for lower velocity
bottle rockets with small nozzles.

The FTC rocket's altitude differed
significantly from simulator
predictions. We will have to investigate
why this is the case, but as can be seen
in one of the photographs and a video as
well, the rocket bent quite
significantly on takeoff. The
rocket is not very stiff so we didn't
find this surprising. This bending is
most likely inducing significant amount of
drag and hence lower altitude. At 180 psi we are
still below the burst pressure of the
naked FTC tubing, so we should be able
to push the pressure beyond the 200psi
mark with the strapping tape
reinforcement. We had only done pressure
tests to 180 psi of the assembled rocket
before launching it so we did not want
to go above that pressure on launch day.
We will now test it to higher pressures
before launching again. But we will take
it to Doonside to do the higher pressure
launches.

Judging from these flights we will not
be able to push the upper altitude of
the rocket much higher in its current
configuration. The small volume of the
rocket is quite restrictive. And while
we could further reduce the weight by perhaps 50 grams, reduce the
fin size
and reduce overall drag, I
would expect only another 100 feet or so
in altitude at the pressures the rocket
could handle. Switching to T-12 FTC with
better reinforcing is really the only
option for significantly improving
performance and allowing higher
pressures.

These were definitely our highest
velocity launches to date. Simulator
suggests around 230km/h 0.1 seconds
after take off. Peak G-forces are around
70G.

Despite lubricating the release mechanism
and nozzle with silicone grease the
release mechanism was a little stiff on
launch. This may be due to the higher
pressures involved. We may need to add a
longer lever to the mechanism to have
enough force to easily release it.

During the NSWRA open day Phil had
suggested that we should use a swivel on
the parachute line. We didn't have one
handy and so we left it out, but it
turns out we should have followed his
instructions. After the second flight
the main line was quite twisted and it
took us a couple of minuted to untwist
it.

Misc

Now that we have a couple of weeks
holiday, in the short term we will be
focusing on finishing V1.6 of the FC as well
as completing the initial release of the
recovery guide. There are still many links
and cross references to add to it so it will
take a few more days. We will also continue
work on the new Acceleron as there is a lot
of pressure testing to be done. Looking
further forward into 2009 we would like to
continue with the static tests where we left
off a couple of months ago, more work will
be done on the multi-stage rockets with
larger boosters, learning to make
lightweight fibreglass body tubes as well as
finally implementing a couple of projects
that have been in the design phase for at
least half a year. These FTC flights are a
part of the that development cycle. In there
somewhere we also need to find time to work
on the new workshop space that we are adding
under the house.

Launched with
1200mm launch tube. Good flight with
post launch analysis rocket looked a
little bent on the way up. Parachute
deployed around apogee but tangled
and deployed very late. Good landing
without damage.